Methods and apparatus for positioning permanent magnetic blocks

Abstract

A method for positioning permanent magnetic blocks includes providing a plurality of magnetized blocks, positioning the magnetized blocks on a yoke in a row by applying a mechanical force at a first end of the row with a first clamping member and at a second end of the row with a second clamping member, and repositioning the blocks by reducing the mechanical force at the first end by moving the first clamping member away from the first end, and moving the second clamping member toward the second end.

Description

BACKGROUND OF THE INVENTIONThis invention relates to magnetic resonance image (MRI) imaging, and, more particularly, to methods and apparatus for assembling magnetized permanent magnetic blocks used for an MRI magnetic field generator.A highly uniform magnetic field is useful in magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) systems as a medical device or a chemical / biological device. Popular and low maintenance cost MRI systems currently available use a permanent magnet system that creates a middle range uniform field (0.2 to 0.5 Tesla) in a pre-determined space (imaging volume). A permanent magnet system usually uses multiple permanent magnet blocks such as NdFeB to form a single magnetic object and to achieve a desired highly uniform magnetic field in the imaging volume.For a magnetic field generator for an MRI that uses permanent magnets, the magnets used in such an apparatus are often formulated from a plurality of magnetized blocks. However, it is diffic...

AI Technical Summary

Benefits of technology

In one aspect, a method for positioning permanent magnetic blocks is provided. The method includes providing a plurality of magnetized blocks, positioning the magnetized blocks on a yoke in a row by applying a mechanical force at a first end of the row with a first clamping member and at a second end of the row with a second clamping member, and repositioning the blocks by reducing the mechanical force at the first end by moving the first clamping member away from the first end, and moving the second clamping member toward the second end.

Problems solved by technology

However, it is difficult to place un-magnetized material blocks on a yoke plate first and then magnetize each block.

However, it is difficult to position the permanent magnetic blocks on the yoke for an MRI system with high uniformity and accuracy due to the nature of a very large magnetic force acting upon blocks from other blocks and with other magnetic objects (such as the pole piece).

Due to the nature of multiple factors, such as material physical tolerance, magnetic interaction force, assembly tolerance, process variation, etc., the assembled magnetic blocks will not be at a perfect location as intended.

Images